Method of manufacturing a field joint coating

Abstract

A method of manufacturing a Field Joint Coating (FJC) for a pipeline, the method comprising: providing a pipe section to be joined to a similar pipe section or free end of a pipeline, wherein each pipe section is provided with a coating comprising a thermal insulation layer over a length of the pipe section having a protruding section, wherein the end zones of each pipe section are free of thermal insulation, thereby allowing access to the ends of the pipe section and the pipeline to connect the pipe section with the free end of the pipeline, applying an anti-corrosion coating layer on a connection region of the joined ends of the pipe section and the pipeline, heating the protruding section and applying an intermediate coating layer of a thermoplastic material on the anti-corrosion coating layer and the protruding section, applying a thermal insulation layer on the intermediate coating layer.

The invention claimed is: 
     
       1. A method of manufacturing a Field Joint Coating (FJC), the method comprising:
 providing a pipe section to be joined to a further pipe section, wherein each pipe section is provided with a coating comprising:
 a thermal insulation layer which extends over a substantial portion of the length of the pipe section, and 
 an anti-corrosion layer situated underneath the thermal insulation layer, wherein end zones of the pipe section are free of coating, 
 
 connecting the pipe section to the further pipe section to form a field joint, 
 applying an anti-corrosion coating layer on a connection region of the joined ends of the pipe section and the further pipe section, 
 heating at least a part of the thermal insulation layer of the pipe section and the further pipe section on either side of the field joint and applying an intermediate coating layer of a thermoplastic material over the anti-corrosion coating layer and over end faces of the thermal insulation layers on either side of the field joint to provide a continuous intermediate coating layer, wherein the continuous intermediate coating layer is applied over the anti-corrosion coating layer and over end faces of the thermal insulation layers of the joined pipe sections on either side of the field joint, and wherein the continuous intermediate coating layer is allowed to bond with the thermal insulation layers of the joined pipe sections on either side of the field joint, thereby providing a seal across the connection region, and 
 applying a FJC thermal insulation layer on the continuous intermediate coating layer, 
 wherein the thermal insulation layer comprises a protruding section which protrudes from a main part of the thermal insulation layer, wherein the protruding section of the thermal insulation layer has a thickness which is smaller than a thickness of the main part of the thermal insulation layer, 
 wherein the protruding sections of the thermal insulation of the pipe sections comprise an outer side which extends substantially parallel to a pipe axis, and wherein the continuous intermediate coating layer is applied over at least a portion of the outer side of the protruding sections on either side of the field joint. 
 
     
     
       2. The method of  claim 1 , wherein the anti-corrosion layer of each pipe section comprises a protruding section which protrudes from underneath the thermal insulation layer over a length, and wherein applying the anti-corrosion coating layer of the FJC comprises applying a layer of an anti-corrosion coating material onto the connection region and the protruding section of the anti-corrosion layer. 
     
     
       3. The method of  claim 2 , wherein the anti-corrosion layer has a thickness, and wherein the protruding section of the anti-corrosion layer protrudes over a distance of at least twice said thickness from underneath the thermal insulation layer. 
     
     
       4. The method of  claim 2 , wherein the protruding section of the thermal insulation layer has a length which is more than twice a thickness of the protruding section of the thermal insulation layer. 
     
     
       5. The method of  claim 4 , wherein the protruding section of the anti-corrosion layer protrudes over a distance from underneath the protruding section of the thermal insulation layer, wherein the thickness of the protruding section of the thermal insulation layer is substantially uniform, wherein the thickness of the protruding section of the anti-corrosion layer is substantially uniform, and wherein the intermediate coating layer is applied over at least a portion of an end face of the protruding section of the thermal insulation layer. 
     
     
       6. The method of  claim 4 , wherein applying the intermediate coating layer comprises thermally spraying a layer of thermoplastic material onto the anti-corrosion layer and at least a part of the protruding section of the existing layer of thermal insulation, wherein the protruding section of the thermal insulation layer is heated prior to applying the intermediate coating layer, and wherein the intermediate coating layer is fused to the protruding sections of the thermal insulation layers of the pipe sections on either side of the field joint to form one continuous layer across the field joint. 
     
     
       7. The method of  claim 1 , wherein the further pipe section forms the free end of a pipeline.